| 摘要 |
A method for manufacturing a semiconductor device whereby the process is simplified and high performance can be obtained in both a trench-gate transistor and a planar transistor that has a thin gate insulating film when the two transistors are formed on the same semiconductor substrate. In a state in which the gate insulating film ( 11 s) in a peripheral circuit region PE is covered by a protective film ( 12 ), a gate trench ( 18 ) is formed in a memory cell region M, after which a gate insulating film ( 19 ) that is thicker than the gate insulating film ( 11 s) is formed on an inner wall of the gate trench ( 18 ) in a state in which the gate insulating film ( 11 s) of the peripheral circuit region PE is still covered by the protective film ( 12 ).
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